Light beams or optical signals are frequently used to transmit digital data. For example, optical signals are used in fiber optic systems for long-distance telephony and internet communication. Additionally, optical signals are frequently used to transmit data between electronic components on a single circuit board or between electronic components on adjacent or nearby circuit boards.
Consequently, optical technology plays a significant role in modern telecommunications and data communication. Examples of optical components used in such systems include optical or light sources such as light emitting diodes and lasers; waveguides; fiber optics; lenses and other optics; photo-detectors and other optical sensors; optically-sensitive semiconductors; optical modulators, and others.
Such systems making use of optical components often rely upon the precise manipulation of optical energy, usually in the form of a light beam, to accomplish a desired task, such as data communication. This is especially true in systems utilizing light for high-speed, low-energy communication between two nodes.
Often, optical resonators are used to selectively filter, switch, or modulate light beams. Ring resonators are a type of optical resonator. Ring resonators typically have an optical waveguide in a closed loop coupled to a tangential waveguide. When light of the appropriate wavelength is coupled to the loop by the tangential waveguide, the light beam builds in intensity or amplitude over multiple round-trips through the closed loop due to constructive interference. The optical energy then exits the loop into the tangential waveguide. Ring resonators have a characteristic resonant frequency, which requires selective tuning in some systems.
Throughout the drawings, identical reference numbers designate similar, but not necessarily identical, elements.